Styryl isoxazole, styryl pyrazole and styryl isothiazole compounds, and in particular (E)-5-[2-(3,5-di-tert-butyl-4-hydroxyphenyl)vinyl]-3-methylisoxazole, have been described in patent EP 0 245 825. These compounds, which are 5-lipoxygenase and cyclooxygenase inhibitors, can be used in a pharmaceutical composition. They also have sunscreen properties. In particular, they are capable of entering into the composition of pharmaceutical formulations for the treatment of inflammation, arthritis, ulcers, allergies, asthma, psoriasis, cardiovascular states in mammals. They are also used in compositions for protecting against ultraviolet light.
The synthesis of styryl isoxazole derivatives which is described in patent EP 0 245 825 may be carried out according to three approaches. In particular, in the case of (E)-5-[2-(3,5-di-tert-butyl-4-hydroxyphenyl)vinyl]-3-methylisoxazole, the following three synthesis schemes are possible:
I Wittig reaction between the aldehyde (3,5-di-tert-butyl-4-hydroxybenzaldehyde) and 3,5-di-methylisoxazole triphenylphosphonium

II Two-step method comprising:                A reaction between the aldehyde (3,5-di -tert-butyl-4-hydroxybenzaldehyde) and the lithium salt of 3,5-dimethylisoxazole followed by chromatography on a silica gel column.        A second step comprising the treatment of the product resulting from the first step with hydro-chloric acid in methanol to give, after purification on a silica gel column, the desired compound with a yield of 49%.        

III A third approach consists in reacting the aldehyde (3,5-di-tert-butyl-4-hydroxybenzaldehyde) with a 3-carboxylate derivative of isoxazole. After condensation, a dehydration and a decarboxylation are carried out.

The same synthesis schemes make it possible to obtain the styryl pyrazole and styryl isothiazole derivatives.
While the prior art methods make it possible to obtain the styryl isoxazole, styryl pyrazole and styryl isothiazole derivatives, they have the disadvantage of requiring the use of several steps and/or of purifications by chromatography in order to obtain a pure product.